February 12, 2018 UPDATE

I've fixed the SCSI Tape End-Of-File read problems.
The st.c driver has some very bizarre code interpreting the SCSI status blocks.

With that said, I found two issues:

1. When a short-record was read, it was not setting bp->b_resid
to the correct shorter length in certain cirumstances; and

2. When a tapemark was read, bp->b_resid was not being set to
indicate no bytes read.

I've tested the my changes extensively and I'm satisfied that SCSI Tape
functionality is working as it should now.

Current device probe configurations (in order):

Device Type CSR/Port IRQ/PIC Memory
hd Hard Disk 0x1f0 14  
  HD Drive 0 0x104 14  
  HD Drive 1 0x1f0 14  
fd Floppy 0x3f2 6  
sd SCSI Controller 0x330 11  
pc586 PC Network   9 0xd0000
  Alternate 1   5 0xc0000
  Alternate 2   12 0xf0000
wd SMC 80x3 Ethernet 0x280 3 0xd0000
  Alternate 1 0x2a0 5 0xd0000
  Alternate 2 0x2e0 10 0xd0000
  Alternate 3 0x300 10 0xcc000
3c501 3Com #C501 Ethernet 0x300 9  
Mouse Mouse Driver 0x23c 4  
com Serial Port 1 0x3f8 4  
  Serial Port 2 0x2f8 3  
  Serial Port 3 0x3e8 5  
  Serial Port 4 0x2e8 10  
lpr Parallel Port 0x378 7  
wt Wangtek Tape 0x300 5  
  Alternate 1 0x288 5  
  Alternate 2 0x338 5